This invention relates to a device for absorbing the slack of operating wires employed in a device for bending the top end part of an endoscope.
In order to select a suitable passage for the top end part of an endoscope when it is inserted into the body cavity, or to direct the observing window of the endoscope as desired when the body cavity is observed, it is necessary to appropriately change, or bend, the direction of the top end part of the endoscope. For this purpose, a remote operation device is provided in which a pair of wires are extended from the top end part of the endoscope to the manual operating section thereof. The direction of the observing winding can be changed by selectively tightening or loosening the wires at the manual operating section.
However, in the bending operation by the remote operation device, there may be play between the operation of the manual operating section and the bending operation of the top end part of the endoscope. This is highly undesirable, because the operation of an endoscope of this type requires a delicate operation of the top end part. Accordingly, it is necessary that the coupling between the operating sections have no play, and that especially, the wires have no play when they are moved to be tightened.
In view of the flexibility of the passage way through which the wire is inserted, a twisted wire is generally employed. Therefore, the wire is liable to become elongated not only by the repetitive use under tension but also by the untwisting of the wire itself. Accordingly, even if the wires are set tightened in advance, they will slacken with the lapse of time. Thus, it is necessary to provide a slack absorbing device for absorbing the elongation of the wire.
Within the prior art, devices for adjusting the flexing of the bending section of an endoscope are generally known. One such device is described in U.S. Pat. No. 3,892,228. In that prior art patent, a wire sag prevention device shown in FIG. 7 and in the overall system in FIG. 3 comprises a housing 28 containing sliding members 29 coupled to wire elements 17a, 17b and a wire wrapped around pulley 21. A plug member 30 is screwed into the housing and by adjustment thereof, the effective internal length of the cavity in the housing is varied. This restricts the degree of movement of sliding elements 29 to adjust for elongation in the wires. Also, a plugging member 31 can be inserted between plug 30 and one sliding element to further reduce the amount of movement by decreasing, ever further the internal length when the wires have excessively stretched. One of the disadvantages of this device is that "play" exists by having two sliding elements 29 within housing 28. Hence, if the wires 17a, 17b are stretched they may not abut the plug 30 but rather may move within the housing until a sufficient rotation of pulley 21 moves the housing a sufficient distance to engage the slider. Hence, displacement of the housing 28 may not in all cases effectuate corresponding movement of wires 17a, 17b.
Also, with this device, elongation due to untwisting of the wires cannot be prevented because the sliders are not constrained against rotation in the housing. When such untwisting occurs, although further tightening can be accomplished, retwisting of the wires cannot be attained. The use of plug members 31 also adds unnecessary complicating elements easily misplaced or incorrectly positioned.
Since re-adjustment is required for absorbing the elongation of the wire which is caused with the lapse of time, a requirement exists that the slack absorbing device be capable of easy-re-adjustment.
With the device for changing the bending section of the top end part of the endoscope with a pair of wires as described above, the wire which is loosened by the operation of this device is slackened, and more specifically the part of the wire which is extended in the operating section of the device is slackened. It is also necessary to absorb the slack of the wire during the operation of the endoscope as described above.